Futures steady ahead of Yellen speech, Greek vote

* Bank of America's quarterly profit more than doubled as legal costs dropped sharply, driving expenses down to their lowest since 2008. * At her semi-annual testimony on monetary policy, Yellen is likely to face questions on how concerns such as the Chinese stock market slump and the Greece crisis will affect the Fed's decision to lift rates. * Greek Prime Minister Alexis Tsipras is struggling to persuade deeply unhappy leftist lawmakers to vote for a package of austerity measures and